Cha Cheol-soo (Kang Ji-hwan), who has a plain appearance, is a capable police officer, but he lives a sloppy and lazy life, and stinks. The police car is full of dirty clothes that have not been washed for hundreds of years. The smelly socks taken off can stand upright. He is always identified by the victim when mixed in the pile of suspects. One day, his boss gave him and his partners an important task, asking them to send someone to pretend to be a model to mix into the clothing industry and act as a bodyguard for the popular model Kim Sun-ho. The so-called bodyguard is actually a secret search for evidence of Kim Sun-ho's crime. This model with a glamorous appearance secretly engaged in drug trafficking and even killed the police who had previously monitored him. By mistake, Cha Cheol-soo was selected as an undercover agent, and took this opportunity to reunite with Gao Yingcai, the girl he liked in high school. However, in order to become a qualified model, the obese police officer Cha had to start the great cause of weight loss and training under Yingcai's supervision...